Can't set AllowMergeCommit to false on imported repo

[abhinav]

What happened?

I imported a repository with pulumi import and tried to set its AllowMergeCommit option to false. It failed with the following error:

    error: 1 error occurred:
        * updating urn:pulumi:dev::repro::github:index/repository:Repository::test-repo: PATCH https://api.github.com/repos/abhinav/test-repo: 422 Validation Failed [{Resource:Repository Field:m
erge_commit_allowed Code:invalid Message:Sorry, you need to allow the merge commit strategy in order to set the default merge commit message title and message. (no_merge_strategy)}]

Important part:

Sorry, you need to allow the merge commit strategy in order to set the default merge commit message title and message.

Expected Behavior

It should set AllowMergeCommit to false.

Steps to reproduce

1. Create a GitHub public or private repository called "test-repo".

2. Go to Repository settings. Under Pull Requests > Allow merge commits, change Default Message to Default to pull request title and description.

3. In a new github-go project, import this repository.

   pulumi import github:index/repository:Repository test-repo test-repo
   

4. Copy the generated code into main.go and run pulumi up to make sure everything is in order.
   It should report no changes.

   Do you want to perform this update? details
     pulumi:pulumi:Stack: (same)
       [urn=urn:pulumi:dev::repro::pulumi:pulumi:Stack::repro-dev]
   

5. Add AllowMergeCommit: pulumi.Bool(false), to the RepositoryArgs, and delete MergeCommitMessage, MergeCommitTitle since they're no longer relevant.

6. Run pulumi up.
   If you run the update, it will fail with the error:

   error: 1 error occurred:
       * updating urn:pulumi:dev::repro::github:index/repository:Repository::test-repo: PATCH https://api.github.com/repos/abhinav/test-repo: 422 Validation Failed [{Resource:Repository Field:merge_commit_allowed Code:invalid Message:Sorry, you need to allow the merge commit strategy in order to set the default merge commit message title and message. (no_merge_strategy)}]
   

Full program:
Note that this only fails if the repository has already been imported with non-default merge settings first.

package main

import (
	"github.com/pulumi/pulumi-github/sdk/v5/go/github"
	"github.com/pulumi/pulumi/sdk/v3/go/pulumi"
)

func main() {
	pulumi.Run(func(ctx *pulumi.Context) error {
		_, err := github.NewRepository(ctx, "test-repo", &github.RepositoryArgs{
			DefaultBranch:       pulumi.String("main"),
			HasDownloads:        pulumi.Bool(true),
			HasIssues:           pulumi.Bool(true),
			HasProjects:         pulumi.Bool(true),
			HasWiki:             pulumi.Bool(true),
			AllowMergeCommit:    pulumi.Bool(false),
			Name:                pulumi.String("test-repo"),
			Visibility:          pulumi.String("private"),
			VulnerabilityAlerts: pulumi.Bool(true),
		}, pulumi.Protect(true))
		if err != nil {
			return err
		}
		return nil
	})
}

Output of pulumi about

CLI
Version      3.54.0
Go Version   go1.20
Go Compiler  gc

Plugins
NAME    VERSION
github  5.3.0
go      unknown

Host
OS       arch
Version
Arch     x86_64

This project is written in go: executable='/usr/bin/go' version='go version go1.20 linux/amd64'

Current Stack: [...]

TYPE                                URN
pulumi:pulumi:Stack                 urn:pulumi:dev::repro::pulumi:pulumi:Stack::repro-dev
pulumi:providers:github             urn:pulumi:dev::repro::pulumi:providers:github::default
github:index/repository:Repository  urn:pulumi:dev::repro::github:index/repository:Repository::test-repo


Found no pending operations associated with dev

Backend
Name           pulumi.com
URL            [...]
User           [...]
Organizations  [...]

Dependencies:
NAME                                    VERSION
github.com/pulumi/pulumi-github/sdk/v5  5.3.0
github.com/pulumi/pulumi/sdk/v3         3.51.0

Additional context

Details in pulumi up included:

Do you want to perform this update? details
  pulumi:pulumi:Stack: (same)
    [urn=urn:pulumi:dev::repro::pulumi:pulumi:Stack::repro-dev]
    ~ github:index/repository:Repository: (update) 🔒
        [id=test-repo]
        [urn=urn:pulumi:dev::repro::github:index/repository:Repository::test-repo]
      ~ allowMergeCommit  : true => false
      ~ mergeCommitMessage: "PR_BODY" => "PR_TITLE"
      ~ mergeCommitTitle  : "PR_TITLE" => "MERGE_MESSAGE"

Contributing

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[abhinav]

I was able to work around this issue with the following rough steps:

1. Export the stack (pulumi stack export > stack.json`)
2. In stack.json, set all mergeCommitMessage and mergeCommitTitle fields to null
3. Import the result (pulumi stack import < stack.json)
4. Temporarily set AllowMergeCommit: pulumi.Bool(true) in the program above and run.
5. Go back to AllowMergeCommit: pulumi.Bool(false) and run. This should work now.

[guineveresaenger]

It sounds to me that the real issue is this part:

~ mergeCommitMessage: "PR_BODY" => "PR_TITLE"
~ mergeCommitTitle  : "PR_TITLE" => "MERGE_MESSAGE"

At first glance it sounds to me that this is an order-of-operations behavior from the GitHub API, but it is odd that removing those fields would make them be replaced with something else.

I wonder if this is at least somewhat related to integrations/terraform-provider-github#1510?

[guineveresaenger]

I tested this and could reproduce it. It does look like it's trying to set the message and title fields to a default after having already set AllowMergeCommit to false. I'm not sure if this is an upstream bug but will try to verify.

In the meantime, here is a better workaround that doesn't require stack surgery:

1. Leave AllowMergeCommit as true and delete MergeCommitMessage and MergeCommitTitle from your program.
2. Run pulumi up. In your repo settings you should see that the dropdown has been reset to "Default settings"
3. Now you can set AllowMergeCommit to false and it should work as expected.

[abhinav]

• Leave AllowMergeCommit as true and delete MergeCommitMessage and MergeCommitTitle from your program.
• Run pulumi up. In your repo settings you should see that the dropdown has been reset to "Default settings"
• Now you can set AllowMergeCommit to false and it should work as expected.

I'm not completely sure, but I think I tried that too. IIRC, it did not consider setting to default (by deleting those fields) as enough to remove them from the stack state, so when I flipped AllowMergeCommit back to false, it was still trying to ensure that MergeCommitMessage and MergeCommitTitle were set to the default values.

[abhinav]

Just tried it out.
@guineveresaenger, your suggested workaround works!
Thanks!

[guineveresaenger]

I filed integrations/terraform-provider-github#1541 upstream and am marking this as blocked. Please use the workaround for now if you can.